A. O. Smith water heater error codes
How to read the codes
Standard A. O. Smith gas tank water heaters report their status with a light on the gas control valve. Count the flashes between pauses; one flash every three seconds is normal.
All A. O. Smith codes
| Code | Meaning |
|---|---|
| 0 flashes | Light off: pilot out or thermopile not yet warm Full guide |
| 1 flash | Normal operation |
| Solid red | Solid red light: pilot recently went out, thermopile cooling Full guide |
| 2 flashes | Pilot lit but thermopile output too low Full guide |
| 4 flashes | Water temperature too high (high limit tripped) Full guide |
| 5 flashes | Temperature sensor (thermistor) failure Full guide |
| 7 flashes | Gas control valve failure Full guide |
| 8 flashes | Thermopile still producing power with the knob off (pilot valve may be stuck open) Full guide |
| Solid light (steady, not blinking) | Pilot was recently put out and the thermopile is cooling down |
The status light is on the gas control valve near the bottom of the tank. These valves have no power cord: the pilot flame heats a thermopile, which powers the valve. If the pilot is out, there is no light at all.
Power vent, condensing and tankless A. O. Smith models use different displays and codes. The flash codes on this page apply to standard atmospheric gas models with a standing pilot.
No light at all
No light means the pilot is out or the thermopile has not reached operating temperature. After relighting, it can take up to about 90 seconds of pilot operation before the light starts blinking. A. O. Smith's gas valve also requires waiting ten minutes between lighting attempts.
What homeowners can do
- Relight the pilot by following the instructions on the heater's label.
- Count the flashes and match them to the table above.
- Keep flammable products such as gasoline and paint thinner away from the heater.
Most flash codes point to the thermopile, the temperature sensor or the gas control valve, which are jobs for a qualified technician.
If the heater stopped and will not relight, A. O. Smith advises checking the flame arrestor for blue or black discoloration. That can indicate a flammable vapor incident, and the heater should not be used until a technician inspects it.
Common questions
What does a solid red light mean on an A. O. Smith water heater?
It means the pilot was recently put out and the thermopile is cooling down. Wait before relighting.
Why is there no light on my A. O. Smith gas valve?
The pilot is out or the thermopile has not warmed up. Relight the pilot following the label and give it up to about 90 seconds.